A growing interest in miniaturized satellites, having a small form factor launched into low earth orbit (LEO), has led to an increase in both launches of the vehicles and the recognition that earlier techniques for control thereof are inadequate. Due to their smaller size, miniaturized satellites generally cost less to build and deploy into orbit. This allows for large numbers of satellites to be deployed into a constellation and at frequent intervals. As a result, they present unique opportunities for educational institutions, governments, and commercial entities to launch and deploy satellites for a variety of purposes with fewer costs compared to traditional, large satellites. The frequent launch intervals also afford the opportunity to upgrade and specialize satellites within the constellation as hardware advances and/or the mission tasks evolve.
Ground stations on Earth communicate with satellites in orbit—downloading data from satellites and/or transmitting data related to satellite control, task programming and other information. Radio antennas installed at ground stations send and receive radio waves to facilitate these data transmissions.
Due to the LEO of miniaturized satellites the visible time of these satellites from a single, stationary ground station is relatively short. With a satellite in a high inclination orbit, a ground station close to the equator could yield as low as 2 passes of the satellite per 24-hour cycle. Thus, it is important to achieve a strong communication channel to optimally exploit the narrow window afforded by LEO satellites. To this end, ground station antennas are directionally configured with a high gain profile (narrow beam width) (e.g., Yagi, Yagi-Uda) to maximize the radio signal strength and allow for high data transfer speeds.
Ground station antennas are typically mounted on motorized azimuth and elevation rotators (rotors) to maintain the optimal orientation with respect to a satellite by tracking it as it traverses across the sky. This facilitates optimal contact time and clarity between the ground station and the satellite. Changes to azimuth and elevation orientation of the antennas are controlled by a rotor controller.
Antenna rotors are installed and calibrated to known elevation and azimuth values to allow for consistent and accurate adjustments. Over time, through mechanical and environmental stresses imposed on the antenna structure and mechanisms, the rotors eventually drift from their original calibration. This results in inaccurate adjustments to the antenna orientation and satellite tracking, and thus poor ground station-to-satellite communication. Rotors may be manually corrected to compensate for such drift, but this requires on-site visits for each adjustment. The time and cost of on-site calibration of an entire network of ground stations is not sustainable under a low-cost satellite model, or would at least negate the low-cost benefits.
In addition, implementing new ground station hardware is expensive and time consuming. Thus, an improvement can be made to better leverage existing assets and data feeds to solve the above issues and still maintain a low-cost.